[PATCH 41/44] block: switch disk_part_iter_* to use a struct block_device

[Christoph Hellwig]

On Fri, Nov 27, 2020 at 01:53:41PM +0100, Jan Kara wrote:
> On Thu 26-11-20 14:04:19, Christoph Hellwig wrote:
> > Switch the partition iter infrastructure to iterate over block_device
> > references instead of hd_struct ones mostly used to get at the
> > block_device.
> > 
> > Signed-off-by: Christoph Hellwig <hch at lst.de>
> 
> The patch mostly looks good. Two comments below.
> 
> > diff --git a/block/genhd.c b/block/genhd.c
> > index 28299b24173be1..b58595f2ca33b1 100644
> > --- a/block/genhd.c
> > +++ b/block/genhd.c
> > @@ -233,7 +233,7 @@ EXPORT_SYMBOL_GPL(disk_part_iter_init);
> >   * CONTEXT:
> >   * Don't care.
> >   */
> > -struct hd_struct *disk_part_iter_next(struct disk_part_iter *piter)
> > +struct block_device *disk_part_iter_next(struct disk_part_iter *piter)
> >  {
> >  	struct disk_part_tbl *ptbl;
> >  	int inc, end;
> 
> There's:
> 
>         /* put the last partition */
>         disk_put_part(piter->part);
>         piter->part = NULL;
> 
> at the beginning of disk_part_iter_next() which also needs switching to
> bdput(), doesn't it?

That is switched to call disk_part_iter_exit in patch 13.

> 
> > @@ -271,8 +271,7 @@ struct hd_struct *disk_part_iter_next(struct disk_part_iter *piter)
> >  		      piter->idx == 0))
> >  			continue;
> >  
> > -		get_device(part_to_dev(part->bd_part));
> > -		piter->part = part->bd_part;
> > +		piter->part = bdgrab(part);
> 
> bdgrab() could return NULL if we are racing with delete_partition() so I
> think we need to take care of that.

bdgrab never retuns NULL..